Friday, September 09, 2011

CT negative for SAH. Is LP the next step?

That's been the traditional teaching. But that teaching is based on low level data, much of it from the era of early generation CT scanners. This new study in BMJ sought to determine the sensitivity of present day CT scanners as a function of time. The findings:

Of the 3132 patients enrolled (mean age 45.1, 2571 (82.1%) with worst headache ever), 240 had subarachnoid haemorrhage (7.7%). The sensitivity of computed tomography overall for subarachnoid haemorrhage was 92.9% (95% confidence interval 89.0% to 95.5%), the specificity was 100% (99.9% to 100%), the negative predictive value was 99.4% (99.1% to 99.6%), and the positive predictive value was 100% (98.3% to 100%). For the 953 patients scanned within six hours of headache onset, all 121 patients with subarachnoid haemorrhage were identified by computed tomography, yielding a sensitivity of 100% (97.0% to 100.0%), specificity of 100% (99.5% to 100%), negative predictive value of 100% (99.5% to 100%), and positive predictive value of 100% (96.9% to 100%).

The results of this study suggest that if CT using a late generation scanner is done within 6 hours, LP is not necessary to rule out SAH.

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About Me

Originally a traditional internist, I became a hospitalist in the early days of the “movement.” I'll be writing about clinical topics, mainly in hospital medicine. Occasionally politics and other stuff creep in. This content does not constitute medical advice (consult your physician) nor is it authoritative (check primary sources).